当我运行 .Net Framework 3.5 安装程序时，出现以下错误：Windows 无法完成请求的更改。当我尝试在命令提示符中启用 .Net 框架时，出现以下错误：
C:\WINDOWS\system32>dism /online /enable-feature /featurename:netfx3 /all
/limitaccess
Deployment Image Servicing and Management tool
Version: 10.0.18362.1
Image Version: 10.0.18362.86
Error: 0x800f080c
Feature name netfx3 is unknown.
A Windows feature name was not recognized.
Use the /Get-Features option to find the name of the feature in the image
and try the command again.
The DISM log file can be found at
我的应用程序（例如 paint.net、discord、UDK、UE4 和 Windows Troubleshooter）无法运行。
我尝试使用服务器管理器安装 .Net Framework，但这也需要 .Net Framework
UT3 编辑器可以工作:)
这是我收到的错误：
PaintDotNet.exe - .NET Framework Initialization Error
To run this application, you first must install one of the following versions of the .NET Framework:
4.0版
请联系您的应用程序发布者以获取有关获取适当版本的 .NET Framework 的说明。
好的
以下是我的规格：
⌘ Windows 10
Microsoft Windows Version 1903 (OS Build 18885.1001) @ 2019 Microsoft Corporation. All rights reserved
The Windows 10 Pro Insider Preview Operating System and its user interface are protected by trademark and other pending or existing intellectual property rights in the United States and other countries/regions.
Evaluation copy. Expires 08/01/20 00-41
要添加更多重要信息，在“控制面板\系统和安全\系统”中系统类型为“64 位操作系统，基于 x64 的处理器”
编辑：我的一些问题已经得到修复，因为 Framework 4.8 通过更新自动重新安装，.net 1.1 和 2 可以安装，所以只需等待我使用的应用程序添加 .Net 4.8 支持，谢谢大家的回复！
答案1
我在使用 Windows 10 Pro 1909 时遇到了重大问题。
解决方案是移至 Windows Insider 计划（设置\更新和安全\Windows Insider 计划）。
电脑升级到预览版。启动后它立即要求我安装 .NET 2/3.5，这解决了所有问题。
请注意，我尝试在这个问题中应用其他解决方案。我还应用了就地升级到版本 1909 和许多其他选项，但均未成功。
我的计划是让计算机在内部程序中运行 6 个月，然后再返回到“普通用户”。
答案2
Windows 10 Enterprise 1909（从 1903 更新）也存在同样的问题：
DISM 日志：
2019-12-06 22:09:00, Info DISM DISM Package Manager: PID=13756 TID=14532 Processing the top level command token(enable-feature). - CPackageManagerCLIHandler::Private_ValidateCmdLine
2019-12-06 22:09:00, Info DISM DISM Package Manager: PID=13756 TID=14532 Attempting to route to appropriate command handler. - CPackageManagerCLIHandler::ExecuteCmdLine
2019-12-06 22:09:00, Info DISM DISM Package Manager: PID=13756 TID=14532 Routing the command... - CPackageManagerCLIHandler::ExecuteCmdLine
2019-12-06 22:09:00, Info DISM DISM Package Manager: PID=13756 TID=14532 Encountered the option "featurename" with value "NetFx3" - CPackageManagerCLIHandler::Private_GetPackagesFromCommandLine
2019-12-06 22:09:00, Info DISM DISM Package Manager: PID=13756 TID=14532 Encountered an unknown option "featurename" with value "NetFx3" - CPackageManagerCLIHandler::Private_GetPackagesFromCommandLine
2019-12-06 22:09:00, Error DISM DISM Package Manager: PID=13756 TID=14532 Failed to get the Update through CBS. - CDISMPackage::Internal_OpenFeature(hr:0x800f080c)
2019-12-06 22:09:00, Error DISM DISM Package Manager: PID=13756 TID=14532 Failed to get the underlying CBS Feature - CDISMPackage::OpenFeature(hr:0x800f080c)
2019-12-06 22:09:00, Error DISM DISM Package Manager: PID=13756 Feature name NetFx3 is unknown. - CPackageManagerCLIHandler::Private_GetFeaturesFromCommandLine(hr:0x800f080c)
2019-12-06 22:09:00, Error DISM DISM Package Manager: PID=13756 TID=14532 Unknown features were specified on the command-line. - CPackageManagerCLIHandler::Private_GetFeaturesFromCommandLine(hr:0x800f080c)
2019-12-06 22:09:00, Error DISM DISM Package Manager: PID=13756 TID=14532 Failed to get the Feature List from the command line. - CPackageManagerCLIHandler::Private_ProcessFeatureChange(hr:0x800f080c)
2019-12-06 22:09:00, Error DISM DISM Package Manager: PID=13756 TID=14532 Failed while processing command enable-feature. - CPackageManagerCLIHandler::ExecuteCmdLine(hr:0x800f080c)
2019-12-06 22:09:00, Info DISM DISM Package Manager: PID=13756 TID=14532 Further logs for online package and feature related operations can be found at %WINDIR%\logs\CBS\cbs.log - CPackageManagerCLIHandler::ExecuteCmdLine
对我来说，Windows 修复和安装 .Net 4.8 没有区别。
解决方案：
手动安装以下软件包
使用 DISM.EXE 如下：
Dism.exe /online /add-package /packagepath:c:\Windows\servicing\Packages\Microsoft-Windows-NetFx3-OC-Package~31bf3856ad364e35~amd64~~10.0.18362.1.mum
安装所有 6 个缺失的软件包后，添加 netfx3 功能就可以正常工作，即使无需重启！
